report. Seismic reflection profiling, discussed in Part V, can be of value in 

 differentiating various types of glacial deposits. 



58. The material in glacial deposits is known by the general term of 

 glacial drift. Drift is usually divided into two large categories, nonstrati- 

 fied and stratified. Nonstratified drift, called till, is material that has 

 been transported and deposited directly by ice and is usually a heterogeneous 

 mixture of very poorly sorted material lacking apparent stratification. Till 

 deposits occur in many different forms that originated near the ice margins 

 and within the interior of the glacier. Marginal forms may extend for great 

 distances and have a relief of up to 50 m. Terminal moraines form at the 

 maximum point of advance. In valley glaciers, lateral moraines form at the 

 junction of the glacier and confining valley walls. Nonstratified drift 

 accumulates beneath the interior of the glacier in ground moraines that cover 

 much of the glaciated regions. They are characteristically undulating plains 

 with general relief of less than 10 m. Some superimposed features, however, 

 may be considerably higher. 



59. Stratified drift is deposited mostly at the margins of the ice and 

 beyond the ice front. All stratified drift has, to some degree, been trans- 

 ported by flowing water in contrast to the unstratified drift that was depos- 

 ited directly from the ice. Because of this transport by flowing water, 

 stratified glacial deposits are better sorted than till, and in many cases, 

 can make suitable beach fill. The principal geomorphic features associated 

 with stratified deposits are kames, eskers , and proglacial outwash material. 



60. Kames are moundlike features that may have a relief of up to 50 m 

 and diameter of up to 400 m. They are often associated with large circular 

 depressions up to 10 m deep known as kettles. Kames and kettles form a char- 

 acteristic irregular topography, but in many cases, are difficult to differen- 

 tiate from some till deposits without obtaining core samples or geophysical 

 data. 



61. Eskers are sinuous ridgelike features that form in channels, tun- 

 nels, and crevasses in the ice by meltwater transport and deposition of gla- 

 cial material. Eskers are variable in dimensions but, at their largest, can 

 be up to 100 m high, 2 or 3 km wide, and many kilometers long, although the 

 longer eskers may occur in the form of loosely connected segments. In sub- 

 aqueous environments, eskers may be difficult to differentiate from some 

 moraines or non-glacial linear shoals on geomorphic evidence alone. 



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